Predictors of adverse events in uncomplicated type B Aortic Dissection: A Systematic Review with Meta-Analysis

INTRODUÇÃO: A reparação endovascular da aorta torácica (TEVAR) tem sido seletivamente utilizada no tratamento da Disseção Aórtica aguda tipo B não complicada (TBAD); porém, nem todos os doentes beneficiam de TEVAR. A procura por preditores clínicos e radiográficos de alto risco ainda decorre. Esta Revisão Sistemática e Meta-Análise procurou identificar preditores de eventos adversos major durante o seguimento de TBAD não complicada, a fim de identificar quem poderá vir a beneficiar de TEVAR eletiva. AQUISIÇÃO DA EVIDÊNCIA: Foi realizada uma Revisão Sistemática de acordo com as seguintes recomendações: "Preferred Reporting Items for Systematic reviews and Meta-analysis (PRISMA) statement". SÍNTESE DA EVIDÊNCIA: 16 estudos foram incluídos na síntese qualitativa e 10 foram incluídos na Meta-Análise. Vários fatores de risco para a ocorrência de eventos adversos major estão descritos, nomeadamente (1) diâmetro aórtico ≥40 mm, (2) maior diâmetro do falso lúmen (>22mm), (3) patência do falso lúmen, (4) porta de entrada primária com >10mm, e (5) maior número de vasos com origem no falso lúmen. A síntese quantitativa identificou uma associação significativa entre um diâmetro aórtico ≥40 mm e a ocorrência de eventos adversos major (HR=3.56; p<0.00001). A descrição do estado do falso lúmen, diâmetro aórtico e crescimento, e as informações demográficas nem sempre foram ao encontro das recomendações mais recentes da "Society for Vascular Surgery" e "Society of Thoracic Surgeons", publicadas em 2020. CONCLUSÕES: Os doentes com TBAD aguda e subaguda que apresentem um diâmetro aórtico ≥40 mm devem ser submetidos a TEVAR eletiva, uma vez que este é o fator de risco com maior impacto na ocorrência de eventos adversos major (HR). Os restantes fatores de risco apresentam um menor grau de evidência. São necessárias mais recomendações relativas à forma como alguns fatores de risco, resultados a longo-prazo e imagens de seguimento devem ser descritos, por forma a que haja uma seleção mais adequada dos doentes elegíveis para tratamento.INTRODUCTION: Thoracic Endovascular Aortic Repair (TEVAR) has been selectively used for uncomplicated acute type B Aortic Dissection (TBAD); however, not all cases will benefit from TEVAR. A search for high risk clinical and radiographic predictors for complications is ongoing. This systematic review and meta-analysis aimed to identify predictors of major adverse events during follow-up in uncomplicated TBAD, in order to identify who might benefit from elective TEVAR. EVIDENCE ACQUISITION: A systematic review was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-analysis (PRISMA) statement. EVIDENCE SYNTHESIS: 16 studies were included in a qualitative synthesis and 10 in the meta-analysis. Several risk factors associated to major adverse events have been described, including (1) aortic diameter ≥40 mm, (2) greater false lumen diameter (>22mm), (3) patent false lumen, (4) primary entry tear > 10mm, and (5) greater number of false lumen vessels origin. Quantitative synthesis identified an aortic diameter ≥40 mm significantly associated with major adverse events (HR=3.56; p<0.00001). Reporting of false lumen status, aortic diameters and growth, and demographic data was not always congruent with the most recent recommendations by Society for Vascular Surgery and Society of Thoracic Surgeons, published in 2020. CONCLUSIONS: Acute and subacute TBAD patients with an aortic diameter ≥40 mm should be submitted to expedited TEVAR, as this risk factor had the greatest impact on adverse outcomes (HR). Remaining risk factors have weaker evidence. Additional standards of reporting for some risk factors, long-term outcomes and follow-up imaging are needed for better treatment selection

Challenging thermal management by incorporation of graphite into aluminium foams

The recent progress made in active thermal management for electronics demands the development of new open-pore foam materials with excellent thermal performance that result from the combination of high thermal conductivity (≥70 W/mK) and the lowest possible fluid pressure drop. The foams considered to date in the literature do not meet these conditions. In this work, a new class of two-phase composite foam materials, which contain graphite flakes and aluminium, were fabricated by the gas pressure liquid metal infiltration method. These materials were fabricated in two main microstructures: i) aluminium foam with oriented graphite flakes in struts; ii) alternating layers of oriented graphite flakes and aluminium foam. The resulting materials exhibited thermal conductivities within the 60–290 W/mK range, and power dissipation capacities up to 325% higher than those for conventional aluminium foams, with pressure drops kept at convenient values for the most demanding active thermal management applications.The authors acknowledge partial financial support from the “Ministerio de Ciencia e Innovación, Spain” (grant MAT2016-77742-C2-2-P)

Studying the Influential Parameters of an Office Building’s Energy Consumption in North America

The study of building energy consumption has gained immense significance in recent times due to the burgeoning global population and the rapid depletion of energy resources. The present research focuses on analyzing individual parameters that impact building energy usage and devising methods and strategies to reduce energy consumption. An existing office building in Philadelphia was chosen as a reference for simulation in TRNSYS. The factors that affect the building, such as ambient temperature, solar radiation, building envelope, wind speed, and internal gains, were studied and defined according to the existing building standards. Predictive modeling is performed with these inputs for a range of infiltration rates – 0.25 ACH to 0.85 ACH, considering the variability of the parameter. The validated model was subjected to a sensitivity analysis by changing one potential parameter at a time to examine the influence of variation of these parameters on energy usage. The analysis found that the highest energy reduction is executed by replacing double-glazing windows with triple-glazing, with an energy saving of 8.43%. To evaluate the effect of location, a similar sensitivity study is conducted for the same office building in Edmonton and Mexico City. It is found that by replacing the same triple-glazing window with double-glazing, a 12.3% and 5.44% energy saving is achieved for the building in Edmonton and Mexico City, respectively. Henceforth, depending on electricity prices for the respective cities, building in Philadelphia, Edmonton and Mexico City is found to have a monthly savings of $3,133,$7582, and $1,552, respectively (all$ in USD). When considering identical parametric inputs, distinct energy savings are observed across varying locations. These statistics serve as valuable tools for making well-informed and rational decisions regarding investments in energy-efficient technologies and the pursuit of Net Zero energy buildings

Advances in calibration and tracking techniques for pixelated Si Timepix3 detectors

Cette thèse présente un travail ciblé sur les fonctionnalités d’un détecteur Timepix3 (TPX3) en ce qui concerne son utilisation dans le programme expérimental ATLAS-TPX3 au grand collisionneur de hadrons. Une évaluation directe d’un TPX3-Si a été complétée, ciblant plusieurs variables importantes connectées à la mesure du champ de radiation dans l’expérience ATLAS, par des études de retraçage de particules, de spectrométrie, ainsi que de stabilité du détecteur dans cet environment. Tout les résultats sont décrits dans trois publications formant la base de cette oeuvre. Le Timepix utilisé dans cette thèse consiste en un senseur de silicium ayant une épaisseur de 500 μm divisée en 256 × 256 pixels. Chaque pixel a une aire de 55 × 55 μm^2. La première étude porte sur la réponse du détecteur aux fluctuations de température qui ont été étudiées avec le but de déterminer la stabilité du détecteur dans le vide ainsi que dans des environments ou des situations dans lesquels les températures de matériaux entrant en contact avec le détecteur sont variables. Il a été observé que l’augmentation de la température correspond à une croissance dans la taille des amas de pixels. Cela indique que la température réduit le biais effectif interne, ce qui a comme conséquence la diminution de la zone de désertion, par la suite réduisant le champ électrique auquel sont soumis les porteurs de charge. La deuxième étude vise à déterminer les paramètres affectant le regroupement des amas de pixels (clustering). Une technique impliquant l’utilisation de plusieurs faisceaux d’ions est appliquée pour déterminer l’effet de l’énergie ainsi que de la masse d’une particule sur la taille des amas de pixels, avec le résultat que les énergies plus élevées produisent des amas plus grands. Pourtant, il est aussi trouvé que la taille des amas s’accroit aussi selon la masse des ions, bien que plus faiblement. Ces résultats ont des conséquences sur les algorithmes de retraçage qui sont cruciaux pour l’identification des particules. La troisième étude décrit une évolution de la présente technique d’étalonnage en énergie utilisée dans le réseau de détecteurs ATLAS-TPX3. Des protons possédant des énergies entre 2-4 MeV sont utilisés comme particules d’étalonnage, dans le but de réduire la saturation de charge qui se produit aux énergies élevées dans chaque pixel, étant vue dans la technique d’étalonnage conventionnelle. Pour déveloper une extension de cette technique pixel-parpixel, seules les hauteurs d’amas de ces protons sont gardées dans les amas, avec leurs énergies corrigées pour ajuster pour la perte de charge causée par la saturation. Appliquant ce nouvel étalonnage à des protons dans la gamme énergétique de 1,3 à 8,4 MeV, l’énergie reconstruite s’approche de la vraie valeur à 30% en moyenne. Les ions de lithium et de carbone dans la gamme énergétique de 8 à 25 MeV ont également été mesurés avec des énergies reconstruites améliorées.This thesis presents research focused on the functionalities of a Tmepix3 (TPX3) detector as they relate to the operation of this device in the ATLAS-TPX3 experimental program at the Large Hadron Collider. A direct testing of one TPX3-Si detector is performed, focusing on several important variables relevant to the measurement of the radiation field in ATLAS through tracking and spectrometry, as well as stability of the detector in that environment. All results are described in the three publications which form the basis of this work. This Timepix3 detector consists of a segmented Si sensor layer with a thickness of 500 μm divided into 256 × 256 pixels. Each pixel has an area of 55 × 55 μm^2. The first study deals with the detector’s response to temperature fluctuations that were studied with the aim of determining the detector’s stability in vacuum as well as in environments or situations where contact temperatures can vary. It has been observed that temperature increases correspond to larger clusters and lower measured energies for protons measured over the course of this temperature increase. This indicates that, in effect, the temperature reduces the internal bias, decreasing the size of the depletion region and weakening the electric field to which charge carriers are subjected. The second study focuses on parameters that affect clustering. A technique involving the use of multiple ions is developed to determine the respective independent effect of energy as well as particle mass on the sizes of clusters produced by those ions. It is found that energy is the primary driver in determining cluster sizes, with higher energy particles producing larger clusters. However, it is also determined that cluster size increases as ion mass increases, albeit much more weakly. This has implications for tracking algorithms which are crucial to particle identification efforts. The third study focuses on an adaptation to the current conventional energy calibration procedure used in the ATLAS-TPX3 network of detectors. Protons with energies between 2-4 MeV are used as calibration particles in order to reduce the impact of charge saturation that occurs at high per-pixel energies, seen in the conventional calibration. To achieve an extension to the current per-pixel technique, only the cluster heights of these protons are kept in the clusters, with their energies corrected to compensate for the lost charge due to saturation. When applying this new calibration to protons in the energy range of 1.3 - 8.4 MeV, the energy that is reconstructed approaches the true energy by 30% on average. Likewise, Li and C ions with energies in the range of 8 - 25 MeV were also measured with similarly improved energy reconstructions

Controlled laser-induced dehydrogenation of free-standing graphane probed by pump–probe X-ray photoemission

The effects of optical excitation on fully hydrogenated free-standing nanoporous graphene have been characterized by pump–probe X-ray photoemission spectroscopy. Hydrogenated graphene, known as graphane, is characterized by a sp3 hybridization, which induces a sp3 component in the C 1s core level whose intensity can be used to monitor the hydrogen content. Under optical excitation we observe a partial dehydrogenation of graphane, which we attribute to local laser-induced heating; such result allows us to estimate the thermal conductivity of the material, for which we found an upper limit of 0.2 W/(m K), four orders of magnitude smaller than that of graphene. Such stark difference, combined with the possibility of dehydrogenating the graphane substrate via laser exposure, may be exploited to engineer nanostructured heat conduction channels in organic and hybrid organic–inorganic devices. We then explored the sub-nanosecond dynamics of the C 1s core level, which displays a kinetic energy shift and a peak broadening with two different decay constants, 210 ps and 130 ps, respectively. We assign the former to surface photovoltage, and the latter to transient lattice heating

Enhancing the insulation capability of a vaccine carrier box: An engineering approach

Being thermosensitive, Vaccines need storage at specific temperatures of 2-8 \ub0C, and Vaccine Cold chain Carriers are the most widely utilized instruments to carry out rural vaccination drives in Low-income hot climate countries. Several developed designs for the carrier have reported superior performance, but their actual penetration into rural community medicine is limited due to reasons of cost and utility. Thus, the scope for improvement in the design is significant and it is also pertinent to quantify the effect of design features on the performance. Taking shared features possessed by such superior designs, the work presents the impact of geometry, vertically stacked vaccine tray assembly and usage of Phase Change Materials(PCM), on the final passive cooler assembly. A fabricated New Design with given features is cross-compared and analysed with a Market(Original) Design of the same scale and storage capacity. Analysis performed takes a scientific inclination towards Engineering and Insulation aspects of the Vaccine Box. It uses Conjugate Heat Transfer model(CFD simulations), Geometry analysis, experimentally derived Insulation R-values and Temperature monitoring to accomplish this. Secondly, the work presents a systematic design approach to improve upon the conventional design, PCM selection is made using DSC(Differential Scanning Calorimetry) testing, and Material of Construction(MOC) selection is made using Ashby plots based on the results of the simulations. Overall the Fabricated New Design gives an improvement of ≈16% in R-value and ≈17% improvement in the retention time of the specific temperature range, over the conventional (Original) Design

Life span estimation of oil-impregnated paper high voltage current transformers based on long duration tests under simultaneous thermal and electrical stresses

A large number of power system apparatus around the world are over 30 years old in operation. Replacement of power system assets involves high investments. On the other hand, the failure of such equipment causes a high economic impact. The lifespan estimation of high voltage apparatus is an important information to determine the best moment for the replacement. Although the current transformer is an essential component in the electrical power system and its failure may result in serious consequences, there are no accelerated aging tests for this equipment prescribed by technical standards. Life estimation for this equipment is generally made based on field experience, something that cannot be done for new models and/or new manufacturers. In this work, experimental results of life tests performed on reduced models, representing high voltage current transformers with oil-impregnated paper insulation, are presented and discussed. The analysis is based on the application of a multi-stress model, which combines the Montsinger rule and Inverse Power Law. The proposed approach considers the existence of threshold values for electrical and thermal stresses, below them, electrical and thermal degradation are negligible. An order of magnitude for the electrical stress threshold value (E0) and for the electrical aging exponent (n) is obtained from the application of the test results to the model used in this investigation. The scope of the investigation includes several diagnostic tests which are performed after interruptions of the long-duration test. The diagnostic tests include some classical high voltage power frequency measurements, tests on oil samples and finally, dielectric frequency response (DFR), one of the most recent insulation diagnostic techniques. The application of the thermoelectrical multi-stress model to the results indicates that the estimated lifespan for the test samples is about 50 years, that the exponent related to electrical stress n is in the range of 1.3-3 and that the electrical stress threshold E0 is in the range of 1.17 to 1.21 p.u. The results of diagnostic tests carried out as part of this investigation revealed the relevant variation of several parameters along the aging test and, combined with the findings obtained in the autopsy of the failed test samples indicated a dielectric failure caused by the combined action of electrical and thermal stresses. The variations of these parameters are of great value for evaluating the degradation conditions of the insulation over its service life. The cross-analysis of several different diagnostic tests is recommended for decision-making regarding the replacement of equipment in service

THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE THERMOACOUSTIC PROCESS

This thesis presents a study of thermoacoustic processes. Thermoacoustic science, which can serve as a renewable and sustainable source of energy, involves thermodynamics, acoustics and their interactions. This research investigated the thermoacoustic phenomenon through theoretical and experimental investigations. The theoretical study is comprised of two parts. The first part focused on the development of a comprehensive algorithm for the design, development and performance evaluation of thermoacoustic devices. The developed algorithm is capable of designing and optimizing individual thermoacoustic heat engines and refrigerators and coupled engine-refrigerator systems. In the second part of the theoretical study, the theoretical model of thermoacoustic couples predicting stack temperature difference was modified by incorporating more realistic physical processes that were consistent with practical applications. Significant improvement in the accuracy of the stack temperature difference predictions was observed with the modified model as compared to the previous models through experimental validation. Detailed experimental investigations were conducted to enhance the fundamental understanding of the thermo-fluid behavior in thermoacoustic couples. The first part of the experimental study was focused on the investigation of the influence of drive ratio and stack position on the stack temperature field. The results provided the first evidence of the two-dimensional temperature distribution on both end faces of the stack. A physical explanation for the change in the stack temperature difference profile from sinusoidal to sawtooth form with an increase in the drive ratio was provided. It is concluded that the acoustic dissipation in the stack which influenced the stack cold-end temperature was responsible for this behavior. In the second part, experiments were conducted to investigate streaming velocity fields in a thermoacoustic device using a synchronized PIV technique. The results showed that not only the presence of a stack but also the type and geometrical characteristics of a stack can significantly change the structure and magnitude of acoustic streaming. For both stacks, the streaming velocity field in the region adjacent to the hot-end of the stack was stronger with higher spatio-temporal variations as compared to that adjacent to the cold-end of stack, at almost all the drive ratios

Thermal Modeling and Optimization of Lithium-Ion Batteries for Electric Vehicles

This dissertation contributes to the modeling and optimization of Lithium-ion battery’s thermal management for electrified vehicles (EVs). EVs in automotive technology is one of the principal solutions to today’s environmental concerns such as air pollution and greenhouse impacts. Light duty and heavy duty EVs can decrease the amount of the pollution efficiently. EV’s receive their power from installed rechargeable batteries in the car. These batteries are not just utilized to power the car but used for the functioning of lights, wipers and other electrical accessories. The Lithium-ion batteries (LIBs) have attracted a lot of research interest in recent years, due to their high potential as compared to the conventional aqueous based batteries, high gravimetric and volumetric energy density, and high power capability. However, Li-ion batteries suffer from high self-heating, particularly during high power applications and fast charging, which confines their lifetime and cause safety, reliability and environmental concerns. Therefore, the first part of this study consists of the experimental investigation of the charge-discharge behavior and heat generation rate of lithium ion cells at different C-rates to monitor and record the thermal behavior of the cell. A further concern regarding LIBs is strongly dependent on the quality and efficiency of battery thermal management system. Hence, this is extremely important to identify a reliable and accurate battery management system (BMS). Here in the second part, we show that thermal management and the reliability of Li-ion batteries can be drastically improved using optimization technique. Furthermore, a LIB is a compact system including high energy materials which may undergo thermal runaway and explode the battery if overcharged due to the decomposition of battery materials within the electrolyte and electrodes that generate flammable gaseous species. The application of this kind of technology needs many laboratory experiments and simulations to identify the fundamental thermal characteristics of the system before passing it to the real use. An accurate battery model proposes a method to simulate the complex situations of the system without performing time consuming actual tests, thus a reliable scheme to identify the source of heat generation and required parameters to optimize the cell performance is necessary. For this reason, the latest phase of this research covers the development and comparison of a model based on adjustable design parameters to predict and optimize battery performances. This kind of model provides a relationship with the accuracy and simplicity to estimate the cell dynamics during charge and discharge